/*
 * Copyright 2012-2019 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.springframework.data.mybatis.dialect.pagination;

import java.util.Locale;

/**
 * .
 *
 * @author JARVIS SONG
 * @since 2.0.0
 */
public class TopLimitHandler extends AbstractLimitHandler {

	@Override
	public boolean supportsLimit() {
		return true;
	}

	@Override
	public String processSql(String sql, RowSelection selection) {
		if (LimitHelper.hasFirstRow(selection)) {
			throw new UnsupportedOperationException("query result offset is not supported");
		}
		final int selectIndex = sql.toLowerCase(Locale.ROOT).indexOf("select");
		final int selectDistinctIndex = sql.toLowerCase(Locale.ROOT).indexOf("select distinct");
		final int insertionPoint = selectIndex + ((selectDistinctIndex != selectIndex) ? 6 : 15);

		StringBuilder sb = new StringBuilder(sql.length() + 8).append(sql);

		sb.insert(insertionPoint, " TOP " + selection.getMaxRows());

		return sb.toString();
	}

}
